A BRUTAL MURDER - POLICE HAVE DNA EVIDENCE, BUT CAN'T MATCH A KILLER - SO HOW DID A YOUNG FILMMAKER END UP A MURDER SUSPECT?

"48 Hours" Investigates in "The DNA of a Killer," Saturday, Dec. 16

Nearly two decades after an Idaho teenager was killed, New Orleans filmmaker Michael Usry, the producer of a short film about a brutal death, found himself the suspect in the teen's murder. What led police to the auteur?

Anne-Marie Green and 48 HOURS investigate the 1996 death of Angie Dodge and the unusual police hunt for her killer that led to Usry, in an updated encore of "The DNA of a Killer" to be broadcast Saturday, Dec. 16 (10:00 PM, ET/PT) on the CBS Television Network.

"Nobody ever thinks that they're going to get picked up by the police and taken into an interrogation room and questioned about a murder," Usry tells 48 HOURS. "When it happens to you, it's definitely a game-changer."

Angie Dodge was murdered in 1996. The killer left behind DNA, a semen sample on her body, which police and her family believed would lead quickly to the person who murdered the teen. Of all the men Dodge knew, none of the DNA that police tested was a match. But after 28 hours of interrogation over 23 days, Christopher Tapp, who knew Dodge, confessed to being there when she was killed. He said he participated while others stabbed her. One of the men, he said, was named Mike. But with no last name it seemed like a dead end. Tapp was convicted of killing Dodge. Officially, though, the murder case was still open because Tapp's DNA didn't match the man who left semen at the crime scene.

In 2014 police took a new approach. They searched a public database that had been bought by Ancestry.com. The goal was to find a close match, perhaps a family member to the alleged killer, through a process called familial searching. The search resulted in a partial match. Armed with a warrant, police got Ancestry.com to reveal the name of the anonymous man behind the DNA sample. His name was Michael Usry Sr. and it turns out he had a son Michael Usry Jr. Police wondered if Usry Jr. could he could be the "Mike" that Tapp told them about.

Usry Jr. is a filmmaker with a short film titled "Murderabilia." Given the subject of Usry's film, along with the fact he'd been through Idaho Falls at one point in his life, police thought they had their man. But in truth, Usry Jr. had nothing to do with the 1996 death of Dodge and was officially cleared. His story raises questions about what happens when police use publicly available DNA databases to solve cases - and what goes on when an innocent man is tagged as a suspect.

Usry Jr. has now joined with Angie Dodge's mother to search for the man who left his DNA at the scene. And through their search they have come to believe that Chris Tapp, the man who was serving time for the murder after his confession, was in fact innocent.

Now, the case has taken another turn as investigators work with technology that allows scientists to create facial sketches by using DNA. Can that lead to the killer? Green and 48 HOURS have the latest.

48 HOURS: "The DNA of a Killer" is produced by Judy Rybak, Elena DiFiore, Lindsey Schwartz and Chris O'Connell. Linda Martin is the update producer. Gregory McLaughlin is the producer-editor. George Baluzy, Michael McHugh and David Spungen are the editors. Patti Aronofsky is the senior producer. Nancy Kramer is the executive story editor. Susan Zirinsky is the senior executive producer.

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